Arduino Uno Rev 3 + Wifi Shield - No data being sent

Hi, I'm hoping someone might be able to help.

I have previously got the Wifi Shield connected to the Arduino and working fine - could connect to my home wifi, and could see the "Link", "Error" and "Data" lights all working.

Today, I plug it all together, and can no longer connect to my home networks, using scripts that were working fine last time I tried them.

The pins are working, and I can get LEDs to light up fine, so I think the board is connected to the Uno board ok, but it just doesn't seem to be connecting to the wifi properly.

I'm fairly new to this, so any help or pointers (or even tips on how to debug this sort of problem) would be much appreciated.